Various techniques have been devised in the past for analyzing the cause of automobile accidents. In many situations, eyewitness accounts are lacking; or, if available, are subject to considerable speculation and fail to provide an accurate picture of speed, acceleration of the vehicle or vehicles involved, braking, change in direction or use of turn signals. Accident modeling is perhaps the most common means of recreating an accident and which, with the aid of expert testimony, can be successfully employed in determining the possible cause of an accident. In accident modeling, however, much has to be deduced from the extent of damage caused by the impact and, particularly in the absence of eyewitness accounts of the accident, does not afford a complete picture of the dominant or major cause of the accident; nor is it always possible to deduce from the extent and nature of damage all of the factors which may have contributed to the accident. This is especially true with respect to the performance of each vehicle involved over a preselected time interval prior to and during the accident. For instance, although vehicle or accident modeling may reveal the total force of impact between two vehicles, such is not always an accurate gauge of the speed of each car prior to the accident, or whether one vehicle or the other was accelerating or decelerating immediately prior to the accident. The same is true of braking, steering or turning, or whether one or both cars employed turn signals or headlights.
Systems have been devised in the past for recording certain of the above and other performance characteristics of vehicles. For example, speed and distance recorders are in widespread use for ground vehicles, aircraft as well as ships. Representative patents disclosing such systems are U.S. Pat. Nos. 1,252,102 to R. Erdle; 1,827,988 to P. A. Kourtzman; 1,484,125 to G. B. Frazer; 1,910,191 to J. R. M. Tisdale; 2,976,102 to B. F. Palmer; 3,706,097 to A. Bauer; 3,132,916 to F. Muller; and 3,855,599 to N. Helmschrott et al. Moreover, course and log recorders for recording the direction as well as distance, time and speed over long term intervals are often employed on vessels in aircraft, such as, disclosed in U.S. Pat. Nos. 886,788 to T. M. Foote; 1,701,582 to G. Mengden; 2,906,581 to T. P. Huden; 2,916,202 to A. W. Beishline; 2,959,459 to J. J. Ryan; and U.S. Pat. No. 3,075,192 to J. J. Ryan et al. Other systems are capable of detecting abrupt turning, braking and stops, as suggested in U.S. Pat. Nos. 2,487,819 to M. D. Markley et al; 3,099,817 to H. C. Kendall; 3,160,463 to F. Moscarini; 3,792,445 to R. M. Bucks et al; 3,206,116 to J. Short; 3,983,565 to E. Koller; 3,067,061 to J. E. Juhasz; 4,188,618 to E. S. Weisbart; 3,213,459 to F. R. Bramsch et al; 4,184,166 to H. H. Olson; 4,212,016 to H. Ruhl; and 3,383,696 and 3,624,660 to M. Fichter. Nonetheless, none of the systems referred to are capable of monitoring or sensing a broad range of performance characteristics of a vehicle so as to closely correlate or coordinate such data into a dense, high resolution recording over a limited time interval. In this respect, it is important that provision be made for automatic erasure of the information recorded at predetermined time intervals so that a specific time interval preceding and during an accident can be readily accessed and examined in determining the cause of an accident. Specifically, it should be possible to be able to determine actual ground speed, acceleration, deceleration or G forces, braking, steering, use of turn signals and headlights all in a closely coordinated sequence of events or readings over a limited time interval so as to be able to determine accurately the total performance and operating characteristics of a vehicle in relation to a specific time period. Special purpose devices have been suggested for use as a part of a recording system for the purpose of erasure of information, such as, that recorded on magnetic tape. In general, however, such devices have been intended more for use in erasing after extended time intervals, such as, at the end of a trip.
As previously mentioned, specifically in connection with accident analysis, it is highly desirable to record a number of diverse conditions or parameters representing the performance characteristics of a vehicle within a limited recording area and over a limited time interval so as to be able to record such conditions in real time and to permit automatic erasure at selected time intervals whereby only that time interval immediately preceding, during and after the course of an accident will be recorded and remain available for evaluation.